Fig. 1.
Response patterns and recording sites of lumbosacral spinal neurons to graded colorectal distensions (CRD). A: low-threshold excitatory response to CRD. B: high-threshold excitatory response to CRD. C: Black circles (●) represent neurons excited by CRD and inhibited by L2-L3 SCS. Open circles (○) represent neurons excited by CRD and not responding to L2-L3 SCS. C': Black squares (■) represent neurons excited by CRD and inhibited by C1-C2 SCS. Open squares (□) represent neurons excited by CRD and not responding to C1-C2 SCS. C": spinal laminae of gray matter of L6 segment drawing from Molander et al. (1989). I-X, laminae; Liss, Liss's tract; LSN, lateral spinal nucleus; Pyr, pyramidal tract; IM, intermedial nucleus.